1. Field of the Invention
The invention relates to a method for preparing high optical density solutions of silver platelet nanoparticles (e.g., nanoplates) and to nanoparticles, solutions and substrates prepared by said methods.
2. Description of the Related Art
Nanoparticles, including nanospheres, nanorods, nanowires, nanocubes, nanoplates, as well as other shapes can be synthesized from a range of materials. In one embodiment, a platelet nanoparticle is a nanoplate. Nanoparticles made from metals including gold and silver have unique optical properties which can be tuned to interact with light throughout the electromagnetic spectrum due to the localized surface plasmon resonance supported by these nanomaterials. Technologies that take advantage of the unique optical properties of silver nanoparticles include, but are not limited to, diagnostic, photonic, medical, and obscurant technologies. A subset of these technologies including photothermal tumor ablation, hair removal, acne treatment, wound healing, and antimicrobial applications among others, may use solutions of nanoparticles with high optical densities. Silver nanoplates, which are also known as silver platelet nanoparticles or nanoprisms, are of particular interest for technologies that utilize nanoparticle optical properties due to their tunable spectral peaks and extremely high optical efficiencies. While methods of fabricating silver nanoplates via photoconversion (Jin et al. 2001; Jin et al. 2003), pH-controlled photoconversion (Xue 2007), thermal growth (Hao et al. 2004; Hao 2002; He 2008; Metraux 2005), templated growth (Hao et al. 2004; Hao 2002), and seed mediated growth (Aherne 2008; Chen; Carroll 2003; Chen; Carroll 2002, 2004; Chen et al. 2002; He 2008; Le Guevel 2009; Xiong et al. 2007) have been developed, these methods generate relatively dilute solutions with correspondingly low visible and near-infrared optical density.